The present invention relates to irrigation control systems and, more particularly, to a system and method of initiating an irrigation event of plants that are grown in containers.
Many horticultural crops are typically grown in containers, such as pots, bags, and rockwool slabs, having growth media, where the roots are confined to a very limited area. The plants or crops and the growth media are generally collectively referred to here as the plant media systems. To ensure adequate irrigation, these plants or crops are often excessively irrigated, resulting in a waste of water and fertilizer contained in the water. Excessive irrigation also results in runoff containing high amounts of nutrients, such as nitrates and phosphates, and soil applied pesticides, all of which are potential sources of pollution to the environment. This is of concern, since laws are now requiring much stricter control of runoff which may contribute to environmental problems.
Many techniques have been utilized in the past to measure moisture in plant media systems to control irrigation, but the hydraulic characteristics of most media make the measurement of moisture content difficult. In situ sensors utilizing principles of electrical conductivity, thermal diffusivity, soil suction, and microwave attenuation have been used to measure moisture content in plant media systems. However, while theoretically sound, these principles are difficult to apply in controlling irrigation systems. Furthermore, while weighing lysimeters have been used to extrapolate weight changes to evapotranspiration, none have been effective in taking into account extraneous weight changes due to drainage, and hysteresis or the varying moisture storage capacity of growing media, and changes in plant weight as a result of fruit set, vegetative growth, pruning, and harvesting. It is essential to take these factors into account to accurately determine weight change due to evapotranspiration.
Accordingly, there has existed a definite need for an irrigation control system for overcoming these problems and for precisely controlling irrigation based on measured evapotranspiration. There further has existed a need for an irrigation control system which allows for compensation for weight changes due to factors such as fruit set, vegetative growth, pruning and harvesting. The present invention satisfies these needs and provides further related advantages.